Russian Zvonareva, decked out in host Qatar's colors of maroon and white, had much more verve and zip than her struggling Serbian opponent, who offered only fleeting resistance in the first set before capitulating in the second, losing 6-3, 6-0.

Jankovic had exited her two previous tournaments in the second round citing ill health, and was clearly under the weather against the world number two in the White Group opener at the Khalifa Tennis Complex.

Leading 4-2 in the first set, Zvonareva ran the legs off Jankovic in the seventh game, though the Serbian fought off several break points to eventually hold serve.

That would prove a temporary reprieve, however, as Jankovic would fail to win another game, Zvonareva winning the next eight in a row to wrap up the match in style.

In the maroon group, world No. 1 Wozniacki is taking on Elena Dementieva while French Open champion Francesca Schiavone plays Sam Stosur in the evening's final match.

In Vienna, former No. 1 Thomas Muster lost his first match back on the ATP Tour after 11 years away on Tuesday, but afterwards insisted he still plans to press ahead with a comeback next season.

The 43-year-old Muster, who won the French Open in 1995 and became No. 1 the next year, was beaten 6-2, 7-6 (5) by fellow Austrian Andreas Haider-Maurer at the Bank Austria Trophy.

“I'll keep training hard and plan to enter 20 to 25 events from March,” Muster said of his future plans.

Muster returned to competitive tennis on the second-tier Challenger circuit in June before accepting a wild card for the Vienna event. He had been drawn to face Ernests Gulbis in the first round before the 24th-ranked Latvian pulled out on Monday for personal reasons.

“I am relieved despite losing as I gave my best and played pretty well,” Muster said. “A third set would have been great but well done to Andreas.” The result means that Jimmy Connors remains the oldest player to win a match on the ATP Tour by reaching the quarterfinals in Halle, Germany, in 1995 at age 42.

Earlier Tuesday, Germany's Michael Berrer upset sixth-seeded Guillermo Garcia-Lopez 6-3, 4-6, 7-5.

The 29th-ranked Spaniard, who won in Bangkok and reached the quarterfinals in both Tokyo and Shanghai earlier this month, double-faulted 12 times.

Berrer next plays Pablo Cuevas of Uruguay, who defeated Thiemo de Bakker of the Netherlands 7-6 (6), 1-6, 6-4.

Lukasz Kubot of Poland broke his seven-match losing streak by beating James Blake of the United States 6-4, 6-4 and set up a second-round match against top-seeded defending champion Jurgen Melzer.

Also, Santiago Geraldo of Colombia defeated Belgium's Xavier Malisse 6-4, 1-6, 6-1 and Grega Zemlja of Slovenia rallied to beat Marsel Ilhan of Turkey 4-6, 6-1, 7-5.